Following Burge, many anti-individualists suppose that a subject can possess a concept even if she incompletely understands it. While agreeing that this is possible, I argue that there is a limit on the extent to which a subject can incompletely understand the set of concepts she thinks with. This limit derives from our conception of our ability to reflectively evaluate our own thoughts or, as Burge puts it, our ability to engage in critical reasoning. The paper extends Burge’s own work on critical reasoning. He argued that critical reasoning imposes a limit on the extent to which we can be mistaken about what thoughts we are having; in general, we can know non-empirically what we are thinking . He does not explicitly consider whether critical reasoning also imposes a limit on incomplete understanding of thoughts